Ik Onkar

Ik Onkar (Gurmukhi: ੴ, ਇੱਕ ਓਅੰਕਾਰ; Ikk Ōankār Punjabi pronunciation: [ɪkː oəŋkaɾ]) is the symbol that represents the One Supreme Reality and is a central tenet of Sikh religious philosophy.Ik (ਇੱਕ) means one and only one, who cannot be compared or contrasted with any other, (ਓਅੰਕਾਰ) is the one universal ever flowing divine melody and existential unstuck never ending sound of God.

To simplify Ik means one, Oang the creator and Kar means the creation. So the creator and his creation are not different and He the supreme creator resides everywhere and in everything.

The sound is Oang (anhad naad) and Kar is the never ending continuation of Oang sound. This melody manifests in billions of galaxies and universes and leads to protect and preserve. Ultimately, everything gets merged back into this sound; this has happened countless times before.

It is a symbol of the unity of God in Sikhism, meaning God is One or One God, and is found in all religious scriptures and places such as Gurdwaras. Derived from Punjabi, Ik Onkār is the first phrase in the Mool Mantar referring to the existence of "one constant divine melody" which is proved by Gurbani itself in:

ਓਅੰਕਾਰ ਏਕ ਧੁਨਿ ਏਕੈ।।
Oangkar one and only divine melody
ਏਕੈ ਰਾਗੁ ਅਲਾਪੈ।।
One melody is tuned
ਏਕਾ ਦੇਸੀ ਏਕੁ ਦਿਖਾਵੈ ਏਕੋ ਰਹਿਆ ਬਿਆਪੈ।। ਮਹਲਾ ੫
One is his land, one way he shows and that one is omnipresent.
ਅੰਗ ੮੮੫
Page 885 (Shree Guru Granth Sahib Ji)
ਓਅੰ ਆਦਿ ਸਰੂਪੈ।।
ਓਅੰ ਗੁਰਮੁਖਿ ਕੀੲੋ ਪਸਾਰਾ।।

It is found in the Gurmukhi script and is consequently also part of the Sikh morning prayer, Japji Sahib. It is a combination of two characters, the numeral ੧, Ikk (one) and the first letter of the word Onkar (Constant taken to mean God) - which also happens to be the first letter of the Gurmukhī script - an ūṛā, ੳ, coupled with a specially adapted vowel symbol hōṛā, yielding ਓ.

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Wikipedia